An ongoing goal of biomaterials research is the improvement of compositions from which medical articles, such as medical devices and coatings for medical devices, are produced. An example of such a medical article is an implantable medical device.
In a variety of medical procedures such as, for example, percutaneous transluminal coronary angioplasty (PTCA), stents play an important role. Stents act as a mechanical intervention to physically hold open and, if desired, expand a passageway within a subject. However, thrombosis and restenosis, which may develop several months after a particular procedure, are among the problems associated with the use of stents and can create a need for additional angioplasty or a surgical by-pass operation.
In order to address these problems, stents are being developed to provide for the local delivery of agents. A method of local delivery includes coating the surface of a medical article, e.g., a stent, with a polymeric carrier and attaching an agent to, or blending it with, the polymeric carrier. These agents can be used alone or in combination with other suitable agents. However, there is a continual need for novel polymer coatings for use on drug delivery devices.
Drug delivery stents including bioabsorbable polymeric materials are used in the art. However, with many bio-absorbable polymers, degradation occurs via hydrolysis, which in turn may decrease the pH in the bulk of the polymer. In addition, reports have shown that inflammatory responses can be elicited in a host when a bio-absorbable polymeric material is implanted for a duration of time. If detrimental effects due to degradation of a bio-absorbable polymer did develop, overcoming these detrimental effects with a drug would likely require high drug load concentrations. In addition, many drugs are cytotoxic or cytostatic.
The embodiments described below address the above-identified needs and issues.